The present invention relates to an expandable antivibration bar for use in stabilizing the U-tube sections of heat transfer tubes in the steam generator of a pressurized water reactor.
In pressurized water nuclear reactors, a pressurized fluid is passed through the reactor core and, after being heated, is passed through heat transfer tubes that are positioned in a secondary side of a steam generator where the heat is transferred to a secondary fluid to produce steam that is used to operate a turbine for production of electrical power.
The tubes in the secondary side of the steam generator are of an inverted U-shape design, and since numerous rows and columns of such tubes are present, in a closely packed array, it is important to stabilize the tubes against vibration which causes wear or damage to the tubes. The straight portions of the tubes are supported and stabilized by the use of a series of separator plates, while the U-bend portions of the tubes are supported by antivibration bars. In using the antivibration bars, however, the bars must be slightly smaller than the space between adjacent rows of tubes in order to permit insertion of the bars between such rows. There is still, therefore, a problem which exists due to the size of antivibration bars that can be used in that a potential for some vibration and impacting and wear is still present between the tubes and the bars. Tube wear beyond acceptable limits requires removal of the tube from service, such as by plugging of the tube.